A Storm of Swords

Osney is knighted along with his brother Osfryd after the Battle of the Blackwater despite the fact that neither of them did any actual fighting.[4] He and his brother Ser Osfryd bring Tommen back from Rosby after the death of Ser Jacelyn Bywater. All three Kettleblack brothers give evidence against Tyrion in his trial.

A Feast for Crows

Ser Osney and his brothers are ordered by Queen Cersei to dispose of the corpse of Shae. Cersei tells them that what they do with the corpse is of no concern.[5] He is given a horse by his brother, Osfryd, which he names Midnight.[1] Cersei has Osney kill the High Septon, fearing what Lancel Lannister might have told the man. Osney sneaks into the Great Sept and smothers the High Septon with a pillow while he sleeps. As a reward Cersei beds him.

Cersei then sends Osney on a mission. He is to be caught seducing and bedding Queen Margaery Tyrell. Then King Tommen I is to send him to the Wall as punishment, where he can kill the new Lord Commander of the Night's Watch, Jon Snow. Cersei promises Osney a pardon and lordship when both these tasks are completed. Margaery responds to Osney's advances with nothing but teasing, however, so Cersei hatches a new scheme. She tells Osney to go the new High Septon (known as the High Sparrow) and falsely confess to bedding Margaery and two of her three cousins. Cersei then lets him bed her again to make sure he obeys.[6]

During his torture, the Blue Bard is forced to list those he claims are Queen Margaery's secret lovers. Among them is Ser Osney.[6] Osney confesses to the High Sparrow, who has Margaery and her cousins arrested. However, the High Sparrow is suspicious of Osney's confession. He has never heard a confession from a man so pleased to be guilty. The High Sparrow then has Osney tortured to verify his confession. Under that duress, Osney tells a different story, which implicates Cersei in the death of the previous High Septon and in having sexual relations with Osney. This news allows the High Sparrow to arrest Cersei on similar charges to those of Margaery.[7]